JPH0553461A - Image forming device - Google Patents

Abstract

PURPOSE:To suppress the excessive temperature rise of a heating element portion corresponding to a paper nonfeeding section, prevent the futile heat from being applied to the no-image section of a recording material at a paper feeding section, and effectively use electric power as an image heat fixing type image forming device. CONSTITUTION:A heating means is a fixing device bringing a recording material into close contact with a film, moving it to pass through the position of a heating element 1 together with the film, and giving the heat energy to the recording material from the heating element 1 via the film, the heating element 1 has an exciting/heating layer 4 excited from both end sections of the longitudinal direction crossing the shift direction of the recording material, it has branch cable ways 4a-4d branched at preset multiple positions in the middle along the longitudinal direction of the exciting/heating layer 4 and selectively excited and controlled, and the branch cable way to be excited and controlled among the multiple branch cable ways 4a-4d of the heating element 1 is determined based on the size information 17f of the recording material used in the device and the image multiplication information 17d selected and specified in the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, a microfilm reader printer, an image display (display) device and a recording machine.

More specifically, a recording material (electrofax sheet / static paper) is prepared by using a developer (toner) made of a heat-meltable resin or the like by an appropriate image forming process means such as electrophotography, electrostatic recording, magnetic recording and the like. A visible image (unfixed toner image) corresponding to the target image information is formed and carried on the surface of the electronic recording sheet / transfer material sheet / printing paper) by a direct method or an indirect (transfer) method. The present invention relates to an image forming apparatus that heats and fixes a recording material surface as a permanently fixed image.

[0003]

2. Description of the Related Art As an image heating and fixing device, a film is brought into contact with a heating body and moved, and a recording material is brought into close contact with the surface of the film opposite to the heating body side to move and pass the heating body position together with the film. There is known a fixing device of a system (film heating system) in which heat energy is applied to a recording material from a heating body through a film.

This film heating type fixing device uses a linear heating element having a low heat capacity in comparison with other known heat fixing type devices such as a heat roller type, belt fixing type, flash fixing type and oven fixing type. As a result, power saving and shortening of wait time (quick start) can be achieved, and offset can be prevented because the fixing point and the separation point can be set separately. In addition, various drawbacks of other system devices can be solved. It has the advantages of being effective.

According to the applicant's earlier proposal, for example, Japanese Patent Laid-Open No.
The system, device, etc. disclosed in Japanese Patent Laid-Open No. 3-313182 belong to this, and a thin heat-resistant film (or sheet), a moving driving means for the film, and a fixed support of one side of the film with the film inside. A heating member is provided, and a pressing member is provided on the other side of the heating member so as to face the heating member and closely attach the developed image bearing surface of the recording material to be image-fixed to the heating member via the film. Then, the film is moved at a same speed in the forward direction as the recording material to be image-fixed, which is conveyed and introduced between the film and the pressure member at the time of image fixing, and the film is heated by sandwiching the moving film. By passing through the fixing nip portion formed by the pressure contact between the body and the pressure member, the visible image bearing surface of the recording material is heated by the heating body through the film to impart thermal energy to the visible image. Soften and melt, then Irumu and to separate the recording material, or a fixing device or the heating device and base that separating the film and the recording material after the toner is cooled and solidified.

As a heating element, a horizontally elongated heat-insulating / insulating / low-heat-capacity heater substrate having a film widthwise direction is provided in a linear or strip shape along the length of the film contact surface side. A heater having a low-heat-capacity energizing heating resistor (heating element) is used, and the heating element generates heat when electric power is supplied between both ends of the heating element. The entire temperature rises rapidly, and the heat of the heating body is applied to the recording material via the film.

The temperature control of the heating element is performed by a temperature sensor provided on the heating element, a microcomputer of the image forming apparatus main body and a heating element driving (energizing heat generation) circuit, and the temperature is controlled to a predetermined fixable temperature. It Although the heating element is at a high temperature, the film is moved and driven on the heating element at a predetermined speed at least when the heating element generates heat, so local thermal deformation of the film does not occur and stable image fixing is performed. Is executed.

[0008]

[Problems to be Solved by the Invention]

(A) However, when the size width of the recording material used supplied to the apparatus is smaller than the maximum width in the above heating element configuration, it is a difference area between the size width of the recording material used and the effective total length area of the heat generating layer. Also in the recording material non-passing area (hereinafter referred to as the non-paper passing portion) of the heating element, the heat generating layer portion corresponding to the non-paper passing portion has the same unit length as the heat generating layer portion corresponding to the paper passing portion. It generates heat with a predetermined amount of heat generation per hit. The heat generation energy of the heat generation layer portion corresponding to the paper passing portion is consumed for image fixing, but the heat generation energy of the heat generation layer portion corresponding to the non-paper passage portion is not consumed for image fixing, so that heat is accumulated.

As a result, the temperature of the heating element in the non-sheet-passing section tends to rise abnormally (excessive temperature increase), which shortens the durability life due to the heat loss of the heating element or the heat generating layer, and the durability of the fixing film and the pressing member. There is a possibility of causing deterioration of the running property of the fixing film (deviation of film deviation, wrinkles, etc.).

(B) In the case where the effective width of the heat generating layer is equal to the width of the recording material and the middle image area in the longitudinal direction of the recording material is a part, the recording material only takes heat in the non-image area. Is. This wastes heat and consumes extra power. Such a phenomenon often occurs at the time of reduction in which an original is reduced and copied in an electrophotographic apparatus.

The present invention prevents the above situations (a) and (b) from occurring in such a film heating type fixing device. That is, an image forming apparatus provided with this type of fixing device is provided, which does not unnecessarily heat the non-sheet passing portion of the heating body to cause excessive temperature rise, and does not wasteful heat absorption to the recording material of the non-image portion. The purpose is to do.

[0012]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus having the following configuration.

(1) An image having a heat fixing property corresponding to desired image information is formed and carried on the surface of the recording material by the image forming process means, and the formed and carried image is thermally fixed on the recording material surface by the heating means to form an image. An image forming apparatus for obtaining a formed product, wherein the heating means moves a film by bringing the film into contact with a heating body, and bringing a recording material into close contact with a surface of the film opposite to the heating body side to position the heating body together with the film. A fixing device for moving and passing heat energy to a recording material from a heating body through a film, wherein the heating body has an energization heat generating layer whose longitudinal direction is a direction intersecting with the moving direction of the recording material and which is energized from both ends. And a size information of the recording material used for passing the paper through the apparatus, and a branching electric path that branches at a plurality of predetermined positions along the length of the energization heat generating layer and is selectively energized and controlled. Image change selected and specified Image forming apparatus, characterized in that to determine a plurality of branch paths to be controlled energization of the electric branch of the heating body information.

(2) Energization of the heating element is such that the maximum sheet width in the longitudinal direction is energized at the start of energization, and after a predetermined time has passed, the branch circuit decided by the recording material size information used and the image scaling information. The image forming apparatus according to (1) is characterized in that the branch energization is performed.

(3) Depending on the used recording material size information, the branch electric circuit is determined so that the proper heating length range of the heating layer is limited to the length range corresponding to the size information, and the energization is controlled. When the image size of the image scaling information is smaller than the used recording material size, the image heating information is prioritized and the proper heat generation length range of the heating layer is limited to the length range corresponding to the scaling image size. The image forming apparatus according to (1), characterized in that the branch circuit is determined so as to control energization.

[0016]

[Action]

(A) The effective total length area between one end and the other end in the longitudinal direction of the electric heating layer is set to a length dimension corresponding to the width of the maximum size recording material that can be supplied to the apparatus and used. Further, a branch electric path is provided at an intermediate position in the effective full-length area of the energization heat generating layer, which corresponds to the position of the boundary between the paper passing portion and the non-paper passing portion of the heating element when a certain small-sized recording material is supplied.

.. During the image fixing process by supplying the maximum size recording material, the free end side of the branch electric circuit is controlled to be in an open state, and a predetermined voltage is applied between one end and the other end of the energizing heat generating layer to energize. By energizing the heat generating layer, each part of the effective heat generating layer generates heat with a predetermined heat generation amount per unit length, and the image fixing process for the maximum size recording material is executed without any trouble.

.. At the time of image fixing processing by supplying a small-sized recording material, when a voltage is applied to one end of the energization heating layer and the free end of the branch electric path to energize the energization heating layer, it corresponds to the sheet passing portion. The energizing heat generating layer portion (the section from one end of the energizing heat generating layer to the branch point of the branch electric path) generates heat with a predetermined amount of heat generation per unit length, and image fixing processing is performed on the small-sized recording material. ..

In this case, the energizing heat generating layer portion (the section from the branch point of the branching electric path to the other end of the energizing heating layer) corresponding to the non-sheet passing portion is a conducting circuit in which the energizing heating layer portion and the branching electric path are parallel to each other. And the current is shunted to both.

As a result, the amount of heat generated by the portion of the current-carrying heat generating layer corresponding to the non-sheet passing portion is lower than that of the portion of the current-carrying heat generating layer of the sheet passing portion. Therefore, excessive temperature rise of the non-sheet passing portion of the heating element can be suppressed.

A plurality of branch electric paths corresponding to the widths of recording materials of various sizes smaller than the maximum size recording material are provided at required positions in the middle of the energization heating layer, and the heating layer of the heating layer is selected according to the used recording material size information. Overheating of the heating element non-sheet passing area for recording materials of various sizes by deciding the branch circuit and controlling the energization so that the appropriate heat generation length range is almost limited to the length range corresponding to the size information. Can be dealt with.

(B) In this case, when the image size of the image scaling information is smaller than the used recording material size, the image scaling information is prioritized so that the proper heat generation length range of the heating layer is the scaled image size. The branching electric path is determined so that the length of the branching electric path is substantially limited to the corresponding length control. As a result, even in the paper passing portion, unnecessary heat is not given to the non-image portion of the recording material, and electric power can be effectively used as the device.

[0023]

【Example】

(1) Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus of this example is a transfer type electrophotographic copying machine having a fixed document platen-movable optical system type, a rotating drum type photosensitive member, and a variable magnification function. The image forming principle / process and the basic structure itself are publicly known, so that the explanation will be briefly described.

Reference numeral 30 denotes a drum type electrophotographic photosensitive member (hereinafter referred to as a drum) which is rotationally driven in the clockwise direction shown by the arrow. The drum 30 is subjected to a charging process by the charger 31 in the rotation process thereof, and then subjected to slit exposure L of the document image by the movable optical system 32, so that an electrostatic latent image corresponding to the exposed document image is formed on the drum peripheral surface. Is formed. The formed latent image is visualized as a toner image by the developing device 33, and the toner image is sequentially transferred onto the recording material (transfer material) P fed from the paper feeding section 35 by the transfer roller 34. The recording material P having undergone the toner image transfer is separated from the drum 30 and introduced into the fixing device 36, subjected to image fixing processing, and discharged as an image formed product by a paper discharging roller 37 to a paper discharging tray 38. After the image transfer, the surface of the drum 1 is a cleaning device 3
The surface is cleaned at 9 and repeatedly used for image formation.

In the optical system 32, reference numeral 32a is a fixed original glass, on which the original O is placed with the image plane facing downward according to a predetermined placement reference, and the original holding plate 32b is placed over the original O to set it. Reference numeral 32c is a document illumination lamp, 32d is a moving first mirror, and 32e and 32f are moving second and third mirrors.
A mirror, 32g is an imaging lens, and 32h is a fixed mirror. The positions of the imaging lens 32g and the fixed mirror 32h are changed by a moving mechanism (not shown) according to the selected magnification.

In the paper feeding section 35, reference numerals 35a and 35b denote first and second paper feeding cassettes mounted in the paper feeding cassette mounting section of the apparatus. 35c and 35d are papers such as microswitches that detect that the paper feed cassettes 35a and 35b are mounted in the respective paper feed cassette mounting portions and the recording material size (paper size) stored in the mounted paper feed cassettes. It is a size detection means. The detection signal is fetched by the microcomputer MPU16 (FIG. 5). 35e / 3
5f is a paper feed roller and 35g is a registration roller pair.

FIG. 2 shows an operation panel 17 of the apparatus. 17
a is a power switch, 17b is a copy number setting key, 17c
Is a number display, 17d is a magnification specifying operation key, 17e is a copy start key button, 17f is a recording material size selection key,
17g is a size display part. Magnification change operation key 17
When a desired copy image scaling ratio is selected and designated by d, the scaling information is input to the microcomputer MPU16.

The paper size information input from the paper size detecting means 35c and 35d to the microcomputer MPU 16 is displayed on the recording material size display portion 17g of the operation panel, and a desired size among the display sizes is selected by the selection key 1
By using 7f, the used paper size information is input to the microcomputer MPU16.

(2) Fixing Device FIG. 3 is a schematic diagram of the fixing device 36. The fixing device is of a film heating type.

Reference numeral 7 is a fixing film in the form of an endless belt, which has a driving roller 8 on the left side, a driven roller 9 on the right side,
The low heat capacity linear heating element 1 as a heating element disposed below the driving roller 8 and the driven roller 9 is suspended and stretched between the three members 8.9.1 parallel to each other.

The driven roller 9 also serves as a tension roller for the endless belt-shaped fixing film 7, and the fixing film 7 is rotated at a predetermined peripheral speed in the clockwise direction with the clockwise rotation of the driving roller 8, that is, image formation. The unfixed toner image Ta conveyed from the section (34) side is rotationally driven at the same peripheral speed as the conveying speed of the recording material P carrying the upper surface without wrinkles, meandering, or speed delay.

The drive roller 8 is a metal roller coated with a heat resistant material having a high friction coefficient with respect to the film 7, for example, silicon rubber, and the driven roller 9 has a lower friction coefficient than the drive roller 8, for example, a solid metal. For example, Laura.

Reference numeral 10 denotes a pressure roller as a pressure member having a rubber elastic layer 12 having a good releasability such as silicon rubber. The pressure roller 10 sandwiches the downward film portion of the endless belt-shaped fixing film 7. The lower surface of the heating element 1 is opposed to the lower surface of the heating element 1 by urging means (not shown) with a total pressure of 4 to 12 kg, and the shaft 11 is centered counterclockwise in the forward direction of the conveyance direction of the recording material P. Rotate.

The heating element 1 is a low heating capacity linear heating element having a longitudinal direction in a direction intersecting the plane movement direction of the film 7 (width direction of the film), and includes a heater substrate 3, an energization heating resistor (heating layer) 4, It comprises a temperature measuring element 5 and the like, and is fixedly supported by being attached and held on the heater support 2.

The heater support 2 has a heat insulating property, a high heat resistance, and a rigidity for thermally supporting the heating member 1 with respect to the fixing device and the image forming apparatus. For example, PPS (polyphenylene sulfide), PAI (polyamide imide), PI. (Polyimide) ・ PEEK (Polyether ether ketone) ・
It can be composed of a high heat resistant resin such as liquid crystal polymer or a composite material of these resins and ceramics, metal, glass or the like.

The heater substrate 3 is a member having heat resistance, insulation, low heat capacity and high heat conductivity, and as an example, the thickness is 1 mm and the width is 1.
It is an alumina substrate with a length of 6 mm and a length of 340 mm.

The heat generating layer 4 is formed along the length of the lower surface of the substrate 3 (on the side facing the film 7) along the length thereof, for example, Ag / P.
An electric resistance material such as d (silver-palladium) or Ta ₂ N is applied with a thickness of about 10 μm and a width of 1 to 3 mm by screen printing or the like, and a heat-resistant glass 6 as a surface protection layer is applied to the thickness of about 10 μ
m Coated.

As an example, the temperature measuring element 5 has a low heat capacity such as a Pt film coated on the upper surface of the substrate 3 (a surface opposite to the surface on which the heat generating layer 4 is provided) by screen printing. Is a resistance temperature detector. Alternatively, as the temperature detecting element, a thermistor having a low heat capacity may be arranged in contact with the substrate 3.

In the heating element 1 of the present example, the linear or strip-shaped heat generating layer 4 is energized from both ends in the longitudinal direction to cause the heat generating layer 4 to generate heat over substantially the entire length. Power is AC10
It is 0 V, and the energization power is controlled by controlling the energizing phase angle by an energization control circuit (not shown) including a triac according to the detected temperature of the temperature detecting element 5.

The fixing film 7 generally has a total thickness of 100 μm.
In the following, a single layer or a composite layer film having a heat resistance, a releasability and a durability, which is preferably 40 μm or less, can be used. FIG. 4 is a schematic diagram of the layer constitution of one example of the composite layer film, and this example is a two-layer constitution film. Reference numeral 7a is a heat-resistant layer as a base layer (base film) of the fixing film, and 7b is a release layer laminated on the outer surface (the surface facing the toner image) of the heat-resistant layer 7a.

The heat-resistant layer 7a is a high heat-resistant resin film such as polyimide, polyetheretherketone (PEEK), polyethersulfone (PES), polyetherimide (PEI) or polyparabanic acid (PPA).
Metals such as Ni, SUS, and Al that have excellent strength and heat resistance can be used.

The release layer 7b is made of a fluororesin such as PTFE (polytetrafluoroethylene) / PFA / FEP,
Release layer 7 for heat-resistant layer 7a, which is preferably made of silicone resin or the like
The laminated formation of b is an adhesive lamination of the release layer film, a lamination of the release layer material by a film forming technique such as electrostatic coating (coating), vapor deposition, and CVD, and two layers by coextrusion of the heat-resistant layer material and the release layer material. It can be made into a film.

Since the thickness of the heat-resistant layer 7a is set to be thicker than the thickness of the release layer 7b, the total thickness of the film can be reduced while maintaining the strength of the film, and the heat transfer efficiency from the heating element to the recording material is high. ..

The surface resistance of the release layer 7b is preferably 10 ¹⁰ Ω or less. The resistance value of the surface of the release layer 7b may be lowered by a method of mixing a conductive agent such as carbon black, graphite, or a conductive whisker. In that case, charging of the toner contact surface of the fixing film 7 can be prevented. When the toner contact surface of the fixing film 7 is insulative, the surface of the fixing film is charged and disturbs the toner image on the sheet P, or the toner image is transferred to the fixing film 7 (so-called charging offset). In some cases, these measures can avoid these problems.

(3) Fixing Execution Operation The image forming section 34 operates in response to the image forming start signal, and the recording material P having the unfixed toner image Ta carried on the upper surface and conveyed to the fixing device from the image forming section. Guide 13
Is guided to enter the space between the fixing film 7 and the pressure roller 10 at the pressure contact portion (fixing portion) N between the heating body 1 and the pressure roller 10, and the unfixed toner image surface conveys the recording material sheet P. The heating body 1 and the pressure roller 1 are brought into close contact with the lower surface of the fixing film 7 which is rotated in the same direction at the same speed as the speed and overlap with the fixing film 7 without causing surface deviation or wrinkling.
It passes through the mutual pressure contact portion N with 0 while receiving a clamping pressure. Since the heating element 1 is electrically heated at a predetermined timing by the image formation start signal, the toner image Ta is heated at the press contact portion N and becomes the softened / melted image Tb.

The fixing film 7 has a large curvature at the edge portion S (having a radius of curvature of about 2 mm) of the heater support 2.
The traveling direction turns at a steep angle (the bending angle θ is about 45 °). Therefore, the pressure contact portion N is overlapped with the fixing film 7.
The sheet P, which has been conveyed by passing through the sheet, is curvature-separated from the fixing film 7 at the edge portion S and is discharged. By the time the paper is ejected, the toner is sufficiently cooled and solidified and is in a state of being completely fixed on the sheet P (toner image Tc).

Further, in this example, the heat capacity of the heating layer 4 and the substrate 3 of the heating element 1 is small, and these are adiabatically supported by the support 2, so that the surface temperature of the heating element 1 at the press contact portion N is Since the temperature is raised to a sufficiently high temperature with respect to the melting point of the toner (or the temperature at which the sheet P can be fixed) in a short time, it is not necessary to raise the temperature of the heating element 1 in advance (so-called standby temperature adjustment), which saves energy. Can be realized,
Moreover, the temperature rise inside the machine can be prevented.

(4) Heating Range Control of Heating Body FIG. 5 is a block diagram of a heating control circuit for the heating body 1.

In the figure, 4 and 4a, 4b, 4c, 4
Reference character d denotes an electrically-conducting heat-generating layer formed on the lower surface of the heater body 3 on the heater substrate 3 side, and first, second, third, and fourth branches branched from predetermined positions in the middle of the heat-generating layer. 4 branch electric circuits. Each of these branch circuits 4a, 4b, 4
In the case of this example, c and 4d are energization heating layers made of the same material as the energization heating layer 4. The electric heating layer 4 is formed in a straight line along the length of the substrate at a substantially central portion of the lower surface of the heater substrate 3. Reference numerals 14a and 14b denote conducting electrodes (input terminals) made of a good conductive material such as silver provided at the left end portion and the right end portion of the electric heating layer 4.
Is.

K is the effective total length of the energization heat generating layer 4 between the electrodes 14a and 14b. In this example, the maximum size recording material that can be supplied to the apparatus is the A3 plate, and the length corresponding to the recording material width. It is set to the size.

In the case of this example, recording materials of various sizes are supplied on the basis of a so-called one-sided reference, which is based on the base line a on the left end side of the electric heating layer 4, and the first branch circuit 4a and the second branching circuit 4a. Branch circuit 4b, third branch circuit 4c, fourth branch circuit 4d
Are branched from the portion of the energized heat generating layer 14 at the distances f, h, i, j from the base line a, and each free end is extended to a position corresponding to the right end of the energized heat generating layer 14 or a position outside thereof. Has been formed. Here, each distance f ・ h ・ i ・
j is mini size version, B5 version, A4 in this example, respectively.
The length is set to correspond to the width of the plate and the B4 size sheet.

14c, 14f, 14d and 14e are conducting electrodes made of a good conductive material such as silver provided at the free ends of the first to fourth branch electric circuits 4a, 4b, 4c and 4d.

Energizing heat generating layer 4, each branch electric line 4a, 4b, 4
Since the lower surface of the heater substrate 3 is formed comprising a c · 4d etc. are sliding surfaces of the film 7, it is preferable that a surface protection formed for example Ta ₂ 0 _5, etc. sliding protective layer (6) ..
The temperature sensor 5 is arranged on the upper surface side of the heater substrate 3, that is, on the side opposite to the side on which the electric heating layer 4 and the like are provided, and in the area f which is the minimum sheet passing area.

As described above, when the used recording material size information selected by the recording material size selection key 17f on the operation panel 7 and the scaling information selected by the scaling specifying operation key 17d are input to the microcomputer MPU16, The MPU 16 determines the optimum branch circuit among the plurality of branch circuits for the heating element 1 based on the information, and sends the decode signal to the decoder 15 to select the heating element drive circuit A, B, C, D or E based on the decoded signal. Drive. For example: When the used recording material size information is A3 size paper which is the maximum size width that can be used in the apparatus, and the image scaling information of the selection designation is the same size or enlargement.

In this case, only the heating element drive circuit A is driven and the voltage E is applied only to the electrodes 14a and 14b at both ends of the energization heating layer 4, so that the first to fourth branch electric paths 4a and 4b are respectively applied.
b, 4c, and 4d are kept open, and only the energization heat generating layer 4 is energized to generate heat in the entire length area to fix the image on the recording material.

.. The recording material size information used is A4 size paper, and the image scaling information for selection and designation is A3 → A4, B4 → A4, A3 → B4 even if the image is magnified or reduced (a system in which the image after reduction does not become A4 or smaller) )When.

At this time, the heating element drive circuit A is given priority to the paper size.
And B are driven to drive the electrode 14a and the electrodes 14b and 1
The voltage E is applied between 4d and 4d. That is, the electric heating layer 4
And the third branch electric circuit 4c
The energization system for is also closed. As a result, the area i corresponding to the A4 size is heated and the image on the A4 size paper is fixed.

On the other hand, from the heating layer portion corresponding to the non-sheet passing portion (ki), that is, from the branch point of the third branch circuit 4c to the electrode 14
The portion of the heat generating layer up to b has a current-carrying circuit configuration in parallel with the third branch electric circuit 4c, and a current is shunted between the two, so that the (ki) portion of the portion of the heat generating layer 4 in the region i generates heat per unit length. The amount becomes smaller. Therefore, the excessive temperature rise of the heating body portion corresponding to the non-sheet passing portion (ki) is suppressed.

.. When the used recording material size information is B4 printing paper and the image magnification information of the selection designation is smaller than B4.

In this case, the scaling information has priority. For example, when B4 → B5 is selected, the same E as the heater driving circuit A is driven and the voltage E is applied between the electrode 14a and the electrodes 14b and 14f. That is, since the image to be fixed is only in the area h, the heat generation amount per unit length in the area h is the heat generation amount per unit length in the area h even if the paper size is larger than the area j. To increase.

In short, according to the used recording material size information,
The branch circuit is determined so that the proper heat generation length range of the heat generation layer 4 is limited to the length range corresponding to the size information, and the energization is controlled. In this case, the image of the image scaling information is larger than the used recording material size. When the size is smaller, priority is given to the image scaling information, and the branch circuit is determined so that the proper heating length range of the heating layer 4 is limited to the length range corresponding to the scaling image size, and the energization is controlled. It is a thing.

As a result, it is possible to suppress the excessive temperature rise of the heating element portion corresponding to the non-sheet passing portion, and also to not supply unnecessary heat to the non-image portion of the recording material even in the sheet passing portion, and to supply electric power to the apparatus. It can be used effectively.

(5) Modifications, etc. The heat is applied to the heat generating layer 4 of the heating element 1 by the copy start key button 1
Until the recording material p enters the fixing device 36 after 7e is turned on, electricity is applied between the electrodes 14a and 14b to heat the heat generating layer 4 over the entire length thereof to heat the heating body 1 as a whole.
After that, energization control may be performed on the branch electric circuit determined by the used recording material size information and the image scaling information.

FIG. 6 shows an example of the configuration of the branch electric circuit in the case of recording material supply by central reference conveyance.

The film 7 is not limited to the endless belt shape, but may be a long end film wound in a roll and configured so that the film is fed and run.

[0066]

As described above, according to the present invention, an image having a heat fixing property corresponding to desired image information is formed and carried on the recording material surface by the image forming process means, and the formed and carried image is recorded by the heating means. Regarding an image forming apparatus that obtains an image-formed product by heat-fixing the material surface, it is possible to suppress excessive temperature rise of the heating body portion corresponding to the non-sheet passing portion, and also in the non-image portion of the recording material even in the sheet passing portion. Does not give useless heat, and the power can be effectively used as a device.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus.

FIG. 2 is a plan view of an operation panel unit.

FIG. 3 is a schematic configuration diagram of a fixing device.

FIG. 4 is a schematic diagram of a cross-section of the layer structure of a fixing film.

FIG. 5 is an energization control circuit for the heating layer of the heating element and the branch circuit.

FIG. 6 is a pattern example of a heating layer and a branch electric circuit in the case of central reference conveyance of recording material.

[Explanation of symbols]

 1 Heater 4 Heating layer 14a ・ 14b ・ 14c ・ 14d Branching circuit 7 Fixing film P Recording material 15 Decoder 16 Microcomputer 17d Variable magnification designation operation key 17f Recording material size selection key A ・ B ・ C ・ D ・ E Heating element drive circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kensaku Soka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (3)

[Claims] 1. An image forming process means for forming and carrying a heat-fixing image corresponding to desired image information on a recording material surface, and the formed and carried image is heat-fixed on the recording material surface by heating means to form an image. An image forming apparatus for obtaining an object, wherein the heating means moves a film by bringing the film into contact with a heating body, and bringing a recording material into close contact with a surface of the film opposite to the heating body side to move the heating body position together with the film. A fixing device for passing heat energy to a recording material from a heating body through a film, wherein the heating body has an energization heating layer having a length in a direction intersecting the moving direction of the recording material and energized from both ends. However, it has a branch electric circuit that branches at a plurality of predetermined positions along the length of the energization heat generating layer and is selectively energized and controlled. Selected and specified image scaling information Image forming apparatus, characterized in that to determine a plurality of branch paths to be controlled energization of the electric branch of the heating body between. 2. The heating element is energized at the maximum sheet width in the longitudinal direction at the start of energization, and after a lapse of a predetermined time, the branch circuit determined by the used recording material size information and the image scaling information. The image forming apparatus according to claim 1, wherein the branch energization is performed. 3. The recording material size information is used to control the energization by determining a branch electric circuit so that the proper heat generation length range of the heat generation layer is limited to the length range corresponding to the size information, and in this case, the use is performed. When the image size of the image scaling information is smaller than the recording material size, priority is given to the image scaling information, and the appropriate heat generation length range of the heating layer is limited to the length range corresponding to the scaling image size. The image forming apparatus according to claim 1, wherein the branch circuit is determined as described above to control energization.